Nitroparaffin fuel



Patented Oct. 19, 1954 UNITED STATES PATENT OFFICE NITROPARAFFIN FUELJohn A. Hannum and Joseph N. Epel, Detroit,

Mich., assignors, by mesne assignments, to Borg-Warner Corporation,Chicago, 111., a corporation of Illinois No Drawing. ApplicationSeptember 4, 1947, Serial No. 772,220

devices, although they may also be efficiently used for other primemovers under a variety of circumstances as in aircraft, underwatercraft, land vehicles and stationary installations. Furthermore thesematerials may be used as a source of powerfor particular types ofdevices such as rockets, ram-jets and the like.

Under many operating conditions it is desirable to thermally stabilizethe fuel, as by providing a catalyst to improve its combustioncharacteristics. have been used as catalysts to aid the fuel combustionbut, unfortunately, they also act to some 'extent to lower the normalexplosion temperatures of the material, making it less safe to handleand more liable to premature combustion or explosion than it was beforeaddition of the catalyst. So far as is known, such additives have notheretofore been used with this class of materials without rendering themmaterially less useful as fuels.

A general object of the present invention is to provide an improved fuelof this kind. Another object is to provide an additive for use withfuels, particularly nitro aliphatic fuels, by which their tendency toexplode prematurely in consequence of the addition of the catalyst isdecreased and the safety with which they may be handled improved. Stillanother object is to provide an additive that acts as a catalyst to afuel to im- Heretofore certain fuel additives.

prove its operating characteristics, as by enabling adapted for use withthe fuels that are disclosed in the copending application and that arein the form of liquid nitro aliphatic hydrocarbons, the terms nitroaliphatic and nitroparaffin as hereinafter used being construed hereinto include both mono and polynitro derivatives. Such fuels are limitedto those that contain not more than one nitro group for each carbon atompresent. A preferred form of such fuel is nitromethane,

CH3(NO2), that itself contains much of the oxygen required during thecombustion of the fuel elements in it. It is contemplated that otherfuels from the class of nitro aliphatic liquids may be used in thepresent invention.

Examples of such fuels, in addition to nitromethane, are:

Nitroethane CH3.CH2.NO2 l -nitro pro pane CH3 .CH2.C'H2.NO2

Z-nitropropane CH3) 2CH.NO2 1,1 dinitropropane 2,2 -dinitropropane CH3)20 (N02) 2 1 ,2dinitropropane CHzNOz .CHNO2. CH3 l,3-dinitropropaneCH2NO2.CH2 .CHzNOz l ,l -dinitroethane CHxCH (N 02) 21,2,3-trinitropropane CH2NO2.CHNO2.CH2NO2 1,1, l-trinitropropane C (N02)3 .CHzCHs Such nitro aliphatics included as fuels within the scope ofthis invention include mononitromethane, dinitroethane andtrinitropropane and those nitroethanes and nitropropanes below them inoxygen content but no nitroethanes or nitropropanes that are higher inoxygen content, as for instance dinitromethane. These are all to bedistinguished from aromatic fuels such as the nitrobenzo-ls that aredangerous to handle even by skilled persons to say nothing of personswho are not skilled in this art.

An advantage of using nitromethane or a similar partially nitratedaliphatic hydrocarbon as listed above resides in the fact that itcontains a considerable proportion of the oxygen that is required duringcombustion to burn the carbon or hydrogen in the fuel. This in turn doesnot require the presence of as much air or other oxidizing agent aswould otherwise be necessary. These fuel components are non-brisantnitro aliphatic compounds, non-brisant within the terms of thisdisclosure meaning that the fuel may be burned in contact with chillediron without producing the Munroe efiect.

Although such fuels are non-brisant as defined above, it frequently isdesirable to modify their explosion characteristics. When purenitromethane is heated, it has a threshold explosion temperature of593.6 Fahrenheit. As indicated above, the addition of certain materialsserves to depress to some extent the normal explosion temperatures ofpure nitromethane. Insofar as is known, no additive has been availableuntil the present invention that modifies the explosion characteristicsof nitromethane by suppressing its tendency to explode at or even belowits normal explosion temperatures and still preserves and improves thedesirable properties of nitromethane as a fuel.

The addition of a small amount, from a trace to substantially twopercent by weight of the total fuel mixture, of a chemical compoundwhich may be defined as including an atom of an element withpredominantly metallic properties (metalloid), a plurality of oxygenatoms, and a polysubstituted amine radical both improves the combustionqualities of the fuels outlined above and modifies their explosioncharacteristics in the respect mentioned. Generally speaking, it hasbeen found that chromium and uranium are the two most importantmetalloids insofar as the present invention is concerned, but work todate indicates that tungsten and molybdenum may also be used. Asexamples of the utility of the herein described invention, it is pointedout that when approximately 1% by weight of the pyridine salt of uranylacetylacetonate is added to nitromethane, there is found to be anaccompanying suppression of the tendency to explode at temperaturesbelow 615.1 Fahrenheit, an increase of approximately 20 degrees over thethreshold explosion temperature. In the same way when one percent byweight of dicyclohexylamine chromate is added to nitromethane, thecorresponding value is found to be 691.7 Fahrenheit, an increase ofabout one hundred degrees.

Certain chromium-bearing catalysts have heretofore been added aspreviously mentioned to fuels of the type described, particularlynitromethane, to improve combustion. The materials comprehended by thepresent invention, particularly the .alkyl amine chromates anddichromates, are known to function as catalysts, dicyclohexylaminechromate serving the double purpose of acting as a catalyst ofcombustion and also significantly modifying the explosioncharacteristics of the fuel. In addition to the thermal stabilizersnamed above, various materials in the form of chromate or dichromatesalts derived from reaction of chromic acid with aliphatic and alicyclieamines may be used in a percentage by weight varying from a trace tosubstantially 2% of the total fuel mixture to produce stabilizingresults within the terms of this invention.

It is important that such salts be relatively stable in the fuels towhich they are added and do not readily break down except incident tothe process of combustion. For instance octadecylamine dichromate,hexadecylamine dichromate and hexylamine dichromate all break down intime in nitromethane, somewhat less in nitroethane, and are relativelystable in nitropropane, particularly in the absence of light. The effectof light on all these materials is important and it is desirable tostore them in the absence of light, particularly if the storage periodis of appreciable duration. Chromate and dichromate salts deemed withinthe scope of the present invention as stabilizer additives to fuels, inaddition to pyridine salt of uranyl acetylacetonate, form a group asfollows:

Hexyl, amine chromate or dichromate Cyclohexyl, amine chromate ordichromate 4 Octyl, amine chromate or dichromate Decyl, amine chromateor dichromate Dodecyl, amine chromate or dichromate Dicyclohexyl, aminechromate or dichromate Tetradecyl, amine chromate or dichromateHexadecyl, amine chromate or dichromate Octadecyl, amine chromate ordichromate A fuel mixture made up in accord with the present inventionwill include one or more of the fuels listed above to make up more than98 percent but less than 100 percent by weight of the whole. From twopercent to a trace by weight will be made up of one or more of thestabilizers described herein. Within the limitations described above asto the absence of light and the relatively prompt use after preparation,these materials will act in varying degrees to stabilize the variousnitro aliphatic fuels listed above, which they do by modifying theirexplosion characteristics; furthermore, inasmuch as they break downincident to the process of combustion of the fuel to yield finely.divided metallic oxides, they act as catalysts causing the fuel to burnsteadily and quietly, as distinguished from intermittently, in thecombustion zone.

The use for these purposes of certain of these compounds is claimedspecifically in a divisional application filed in the name of John AI-Iannum on June 9, 1949, under Serial Number 98,157.

We claim:

.1. A fuel mixture comprising at least one liquid nitroparaffincontaining not more than one nitro radical for each carbon atom butpresenting nevertheless the danger of explosion arising out of aninherent capacity for thermal detonation;

the same being selected from a group consisting ,dinitroethane, 1,2,3trinitropropane, and 1,1,1

trinitropropane, and mixtures thereof, to which has been added asuppressant comprising a saltlike organic compound including an atom ofan element with predominantly metallic properties falling in sub-group Aof group VI of the periodic table of elements, a plurality of oxygenatoms connected thereto, and a hydrocarbon-substituted amine radicalwhich salt-like organic compound breaks down incident to the process ofcombustion to yield a finely-divided metallic oxide in the combustionzone.

2. A fuel mixture comprising at least one liquid nitroparafiincontaining not more than one nitro radical for each carbon atom butpresenting nevertheless the danger of explosion arising out of aninherent capacity for thermal detonation; the same being selected from agroup consisting of nitromethane, nitroethane, l-nitropropane, 2-nitropropa-ne, 1,1 dinitropropane, 2,2 dinitropropane, 1,2dinitropropane, 1,3 dinitropropane, 1,1 dinitroethane, 1,2,3trinitropropane, and 1,1,1 trinitropropane, and mixtures thereof, towhich has been added a suppressant modifying the explosioncharacteristics of the nitroparafiin component, said suppressantcomprising an aliphatic amine chromate.

3. A fuel mixture comprising at least one liquid nitroparaffincontaining not more than one nitro radical for each carbon atom butpresenting nevertheless the danger of explosion arising out of aninherent capacity for thermal detonation; the same being selected from agroup consisting of nitromethane, nitroethane, l-nitropropane, 2-nitropropane, 1,1 dinitropropane, 2,2 dinitropropane, 1,2dinitropropane, 1,3 dinitropropane,. 1,1

5 dinitroethane, 1,2,3 trinitropropane, and 1,1,1 trinitropropane, andmixtures thereof, to which has been added a suppressant modifying theexplosion characteristics of the nitroparamn component, said suppressantcomprising a dicyclohexyl amine chromate.

4. A fuel mixture as in claim 3 comprising mononitromethane anddicyclohexyl amine chromate in the proportions of more than 98% of theformer and less than 2%, but more than a trace, of the latter.

5. A fuel mixture as in claim 3 comprising mononitroethane anddicyclohexyl amine chr0- mate in the proportions of more than 98% of theformer and less than 2%, but more than a trace, of the latter.

6 References Cited in the file of this patent UNITED STATES PATENTSOTHER REFERENCES Journal Inst. of Pet. Tech., vol. 1319'27, page 281,article by Egerton et al.

1. A FUEL MIXTURE COMPRISING AT LEAST ONE LIQUID NITROPARAFFINCONTAINING NOT MORE THAN ONE NITRO RADICAL FOR EACH CARBON ATOM BUTPRESENTING NEVERTHELESS THE DANGER OF EXPLOSION ARISING OUT OF ANINHERENT CAPACITY FOR THERMAL DETONATION; THE SAME BEING SELECTED FROM AGROUP CONSISTING OF NITROMETHANE, NITROETHANE,1-NITROPROPANE,2NITROPROPANE, 1,1 DINITROPROPANE, 2,2 DINITROPROPANE, 1,2DINITROPROPANE, 1,3 DINITROPROPANE, 1,1 DINITROETHANE, 1,2,3TRINITROPROPANE, AND 1,1,1 TRINITROPROPANE, AND MIXTURES THEREOF, TOWHICH HAS BEEN ADDED A SUPPRESSANT COMPRISING A SALTLIKE ORGANICCOMPOUND INCLUDING AN ATOM OF AN ELEMENT WITH PREDOMINANTLY METALLICPROPERTIES FALLING IN SUB-GROUP A OF GROUP VI OF THE PERIODIC TABLE OFELEMENTS, A PLURALITY OF OXYGEN ATOMS CONNECTED THERETO, AND AHYDROCARBON-SUBSTITUTED AMINE RADICAL WHICH SALT-LIKE ORGANIC COMPOUNDBREAKS DOWN INCIDENT TO THE PROCESS OF COMBUSTION TO YIELD AFINELY-DIVIDED METALLIC OXIDE IN THE COMBUSTION ZONE.